Saturday, April 18, 2009

A drug commonly used to treat heroin addiction appears to ease thesymptoms of fibromyalgia, a poorly understood but potentiallydebilitating condition that affects up to 12 million people in theU.S. (4 percent of the population), a small pilot study has found.

"We have a medication that seems to have low side effects and seemsto reduce pain and fatigue [in fibromyalgia patients]," says JarredYounger, a pain researcher at Stanford University School of Medicineand co-author of the study appearing today in Pain Medicine. "I thinkthis is a potential treatment to add to the doctor's arsenal," headds, noting that longer studies involving more patients are neededto confirm the results.

Fibromyalgia, a mysterious ailment whose symptoms include chronicwidespread muscle pain, fatigue, sleep problems, anxiety anddepression, often appears between the ages of 34 and 53 and is morecommon in women (affecting 5 percent of women and 1.6 percent of menin the U.S.), the researchers report. The U.S. Food and DrugAdministration (FDA) has approved three drugs for treatingfibromyalgia, but many patients don't respond to them, Younger says.

For 14 weeks, Younger and his colleague Sean Mackey, chief of thepain management division at Stanford, monitored the symptoms of 10women ages 22 to 55 with fibromyalgia before, during and after theytook small doses (4.5 milligrams per day) of naltrexone, a drug thatfor about three decades has been used to wean addicts off of heroinand other street drugs. (Naltrexone works by latching onto nerve cellreceptors where heroin and other opioid drugs would dock, thusblocking their ability to act on the cells and induce a feeling ofbeing high.) Using handheld computers, the women reported theseverity of their daily symptoms on a scale of one to 100 (100 beingthe most severe). Every two weeks, they visited the researchers whodownloaded the data entered in the computers and ran tests to measurethe women's pain thresholds for pressure, heat and cold applied tothe skin.

Their findings: the severity of pain and fatigue fell by 30 percentduring the weeks the women were taking naltrexone compared with thosein which they were taking a placebo. Two of the women said the druggave them vivid dreams and one said she had nausea and insomnia thefirst few nights that she took the pills, but otherwise no sideeffects were reported.

Younger, who suspects fibromyalgia is an autoimmune disorder (inwhich the body's immune system attacks healthy tissue), speculatesthat naltrexone is alleviating fibromyalgia symptoms not by blockingnerve cell receptors but by dampening the activity of microglia—immune cells in the brain and spinal cord that produce pro-inflammatory cytokines, which excite nerve cells responsible forcreating the sensation of pain.

"These results are promising," says Dan Clauw, an anesthesiologist atthe University of Michigan at Ann Arbor's Chronic Pain & FatigueResearch Center who was not involved with the study. But Clauw is notconvinced that naltrexone works by suppressing immune cells; hethinks low doses of the drug might stimulate nerve cells to releasepain-alleviating endorphins.

Regardless of how the drug works, the scientists agree that moreresearch is needed to confirm these preliminary findings. TheStanford team is already about two thirds of the way through a 24-week follow-up study involving 40 patients. And although Youngerhasn't started analyzing the data, he says, "The participants seemhappy…I think it looks good."